Median Irises

The group of bearded irises that are intermediate in size between the dwarf species, their derivatives, and the tall bearded hybrids are called median irises. They are delightful group of irises that are most useful in extending the bloom season. They add new dimensions to the perennial border and deserve a place in everyone's garden.

The four subgroups are standard dwarf bearded irises, intermediate bearded irises, miniature tall bearded irises and border bearded irises. Thus the term "median" refers to all of the bearded irises except the bearded irises and the miniature dwarf bearded irises. The arils and arilbred irises are a different breed of cat altogether.

Before the 1950s, there were small iris varieties that were mostly diploids, that is, they have 16 chromosomes, the original number of chromosomes for the species. Another expression used for diploids is "2n," with half of the chromosomes coming from each parent. These early small irises were derived primarily from Iris lutescens (formerly I. chamaeiris), a native of dry sites in Spain, southern France and Italy.

Later, the dramatic influence in the development of standard dwarf bearded irises and intermediate bearded irises was from 32-chromosome tetraploid (having twice the normal number of chromosomes, or 4n chromosomes) seeds of I. pumila. Later a number of other species, mostly tetraploids, from eastern Europe, including I. cengialtii, were collected and included in the foundation stock of miniature tall bearded, standard dwarf bearded and intermediate bearded irises. The advantages of tetraploids with twice the usual number of chromosomes are increased vigor, increased substance and larger size.

The median irises are all those that are shorter than the tall bearded irises and taller than the miniature dwarf bearded irises, therefore all those that are "median" in height and bloom season.

Standard dwarf bearded irises

Their height: 44-54 in (20-38 cm). Slightly taller than the miniature dwarfs, these come in a vast array of color combinations, many with interesting patterns and thumbprints on the falls. Flowers should stand above the foliage and multiple blooms may in fact hide the leaves altogether when they are in full flower. Often the rhizome sends up several stems, adding to the number of flowers and, with several buds on each stem, they offer an extended flowering season.

Tuck these plants into containers as growth begins and you'll have a burst of color ready to move into a prominent place in your garden when they flower. But put them back in the garden when flowering is over, as that is when they increase rapidly and quickly form a large clump.

These irises will cope with a wider range of environmental conditions than many other bearded irises. They will thrive in northern climates and withstand more wind than taller irises. Standard dwarf bearded irises can tolerate more shade than most bearded irises. In addition, they can tolerate more foot traffic than most irises and so are good choices for garden borders.

The foliage grows throughout most of the season, forming thick attractive mounds whose sword like green leaves add an attractive texture to garden borders. These irises are an asset to gardens of all sorts, but work especially well in mixed beds of low-growing perennials and as border plantings in front of taller plants.

There has been substantial progress in the breeding of standard dwarf bearded irises over the past decade. These irises have come about through the crossing of Iris pumila with tall bearded irises. With I. pumila in the genetic background of so many standard dwarf bearded irises, it is not surprising that pumila spot patterns similar to that ancestor are common. Spots range from small to large and may be highly contrasting or have very little contrast. There also are outstanding varieties without spots, many with contrasting beards. There are some lovely plicata patterns with stitched or dotted petal edges in such combinations as the purple on white 'Royal Decree', burgundy on gold 'Firestorm' and brown on yellow 'Input'.

New flower colors and patterns that are appearing in these irises include better and darker oranges with red beards, pinks with blue beards, chartreuse yellow with red beards and pale blue standards with blue-green falls and red beards. Only the imagination can create standard dwarf bearded irises more astounding than those in reality. They also come in reverse amoenas, that is, flowers with colored standards and white falls, as well as amoenas with white standards and colored falls.

There is such a tremendous variety of flower colors and patterns among the standard dwarf bearded irises that extra study of catalogs is in order to decide how many kinds you can cram into your garden.

Intermediate bearded irises

The intermediate bearded irises are so named because both their height and their bloom season fall in between those of the standard dwarf bearded irises and the tall bearded irises. These median irises must be 16 to 27 inches tall with straight flower stalks that are branched and extend above the erect foliage. The flower stems usually have two branches and five buds on each stalk.

The flowers are 3 1/2 to 5 inches wide and bloom during the period between the bloom seasons of the standard dwarf and tall bearded irises. The intermediate bearded irises have the same height requirements as the border bearded irises but the blooming seasons are different-intermediate bearded irises must have peak bloom earlier than the bearded irises' blooming season. There is some variation in the bloom season, depending upon the variety's breeding and the size of the flowers, with the smaller ones blooming earlier.

The intermediate bearded iris class includes mostly hybrids that are crosses between tall bearded and standard dwarf irises, but some are the result of crosses between bearded irises and species such as Iris aphylla and I. lutescens. Breeders have used I. aphylla to improve intermediate bearded irises fertility, branching and bud count. Although the intermediate bearded irises have strong hybrid vigor, the fertility of these 44-chromosome hybrids is greatly reduced because of their complex genetic structure. As a result, it is less likely that intermediate bearded irises can be crossed with each other to create new cultivars because so many are sterile.

These irises very much resemble their larger tall bearded cousins. They are of good substance and pleasing form, with falls that are flared and rounded and standards that are arched and closed, often with lace or ruffles. Intermediate irises come in the full range of flower colors and combinations that are found in tall bearded irises.

Miniature tall bearded irises

The miniature tall bearded irises are also called table irises and have been bred for small gardens and floral designers. In size, these irises are 16 to 25 inches tall with stalks that are 1/8 to 3/16 inch in diameter and flowers with a combined height and width of not more than 6 inches. The ideal height is 21 to 22 inches rather than the extremes of 16 and 25 inches.

An added attraction to the judging standards of this class is a pleasant fragrance that is important in miniature tall bearded irises. An unpleasant fragrance would make a seedling unacceptable because no one would want it in a table arrangement. The blooms of these irises rise well above the foliage. The flower form of these irises is less ruffled and airier than the larger flowers of tall bearded irises, which gives these irises a look reminiscent of wildflowers.

The miniature tall bearded irises look very much like modern delicate versions of the old-fashioned tall bearded irises, the ones you still see in many old gardens. The plants are miniature versions of tall bearded irises and are different from the intermediate bearded and border bearded irises in that they are slighter smaller in both plant and flower, and thinner and more graceful, with well-branched, wiry stems.

Iris breeders are improving the flower form and broadening the range of colors of these irises using older diploid species and newer tetraploid cultivars. While most of the current table irises derive from older diploid bearded irises, the background of the new pink miniature tall bearded irises is strictly tetraploid hybrids.

Amoenas with their white standards and colored falls, plicatas with stitched or dotted edges on the petals, pale colors and bright colors-all can be found among the miniature tall bearded irises. The ideal iris for flower arranging, the table iris also fit well into perennial beds and borders.

Border bearded irises

Their height: 84-156 in (38-71cm). These flower at the same time as the bearded irises and are lovely planted in front of them as they too are more tolerant of wind and less likely to be buffeted about. Although less well-known than the other types, a good range is available.

Recommended varieties include: 'Batik', unusual streaked white on purple; 'Brown Lasso', butterscotch standards and violet falls edged brown; 'Ingenious', rosy violet standards, with ruby-black falls; 'Pink Bubbles', ruffled and flared flamingo pink flowers.

The judging standards describe border bearded irises as having flower stalks 16 to 27 inches in height with flowers 4 to 5 inches in diameter. Flowers are borne on stiffly erect, branched stems and the leaves are erect and shorter than the flower stalks.

The early requirements for border bearded irises had no specifications for flower size, slimmer stems or narrower foliage. Vigor has proven to be a problem in growing border bearded irises because some cultivars proved to be small only because they lacked the specific environment to reach their genetic potential. When provided with the right site, moisture and nutrients, some border bearded irises grew to be tall bearded irises.

The breeding of border bearded irises slackened during the 1970s, perhaps because this class of irises is so frustrating-a breeder might raise dozens of special crosses only to find that none fit within the border bearded size requirements. Toward the end of the decade, some significant achievements were made, including both color patterns and vigor. Breeders expect that soon border bearded irises will reproduce themselves reliably.

Iris species, including dwarf and larger versions of Iris aphylla-not always a dwarf species especially when used in border bearded iris breeding-I. balkana and I. reichenbachii, now are in the border bearded gene pool and adding their colors and patterns as well as their excellent proportions and small flower size to the breeding stock. As a result, today's breeders are able to raise large crops of border bearded irises in which the majority of young plants fit within the border bearded irises requirements.

Good contemporary border bearded irises should be in good proportion rather than merely a short stem with flowers the size of tall bearded iris blooms. The overall effect should be one of a compact daintiness that is distinctly different from the overall impression one gets from tall bearded irises. These plants will not need staking and their small flowers are excellent for flower arranging. Use border bearded irises to edge a sunny garden or, by definition, as a border.